CN111594116B - In-situ emulsification oil displacement method for low-permeability reservoir - Google Patents
In-situ emulsification oil displacement method for low-permeability reservoir Download PDFInfo
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/16—Enhanced recovery methods for obtaining hydrocarbons
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- C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
- C09K8/58—Compositions for enhanced recovery methods for obtaining hydrocarbons, i.e. for improving the mobility of the oil, e.g. displacing fluids
- C09K8/584—Compositions for enhanced recovery methods for obtaining hydrocarbons, i.e. for improving the mobility of the oil, e.g. displacing fluids characterised by the use of specific surfactants
Abstract
The invention provides an in-situ emulsification oil displacement method for a low-permeability oil reservoir. The method comprises the steps of injecting a preposed protective slug into the low-permeability oil reservoir as a sacrificial agent, and reducing the adsorption loss of a subsequent in-situ emulsified oil displacement agent slug; after the injection of the preposed protection slug is finished, injecting a slug of an in-situ emulsified oil displacement agent with strong emulsifying capacity, weak emulsion stability and moderate low interfacial tension into the low-permeability reservoir, on one hand, starting the residual oil/residual oil in an emulsifying mode, and on the other hand, effectively expanding the micro-sweep efficiency by utilizing the in-situ emulsified oil displacement agent and the emulsion generated in situ by the residual oil/residual oil to temporarily plug the pore throat effect; after the injection of the in-situ emulsified oil displacement agent slug is completed, the oil displacement agent with low flow resistance is injected into the low-permeability oil layer, so that the high-efficiency displacement of residual oil and residual oil in the oil reservoir is realized.
Description
Technical Field
The invention relates to an oil displacement method, in particular to an in-situ emulsification oil displacement method for a low-permeability reservoir, and belongs to the technical field of oil exploitation.
Background
The low-permeability reservoir has the characteristics of poor reservoir physical property, small pore throat radius, strong heterogeneity and the like, and injected water can flow along a high-permeability layer or a crack in the water injection development process, so that the water flooding efficiency is low; because of the characteristics of compact matrix and crack development of a reservoir stratum of the low-permeability oil reservoir, residual oil and residual oil mostly exist in macroscopic and microscopic regions with lower permeability, and the displacement difficulty of the oil reservoir is far greater than that of a conventional oil reservoir; the hypotonic reservoir has a complex pore structure, a small pore throat radius and a large specific surface, and the adsorption and retention loss of the surfactant on the surface of the reservoir rock is serious. Obviously, compared with the conventional oil reservoir, the crude oil in the low-permeability oil reservoir has higher displacement difficulty and has great difference in technical principle. Conventional chemical flooding techniques that are applicable to medium and high permeability reservoirs are not applicable to low permeability reservoirs.
At present, chemical flooding technologies such as surfactant flooding, polymer-surfactant, alkali-surfactant-polymer and the like are successfully applied in industrialization and large-scale mine tests. However, these techniques also expose problems in applications such as erosion and scaling of the reservoir, retention loss of chemical agents, fouling blockage of the reservoir by polymers, difficulty in processing the produced fluids, etc. In the past, many researches are made on surfactants for displacement of reservoir oil of medium-high permeability reservoirs, and the surfactant mainly takes reduction of interfacial tension as a main index (usually the requirement reaches 10)-3mN/m) regardless of the in situ emulsification capacity of the displacement agent. The latest research shows that the residual oil types of different types of oil reservoirs after water flooding are different, and the performance requirements on the oil displacement agent are also different. The ultra-low interfacial tension oil displacement agent only has a good effect on an oil reservoir mainly comprising pore-throat residual oil drops, while for a low-permeability oil reservoir, the type of residual oil after water flooding is mainly microcosmic heterogeneous residual oil, and the oil reservoir has different requirements on the performance of the oil displacement agent from that of a traditional oil displacement agent and is more focused on the in-situ emulsification capacity of the oil displacement agent.
Disclosure of Invention
In order to solve the technical problems, the invention aims to provide an in-situ emulsification oil displacement method which aims at a low-permeability oil reservoir and can effectively improve the oil displacement efficiency.
In order to achieve the technical purpose, the invention provides an in-situ emulsification oil displacement method of a low-permeability reservoir, which comprises the following steps:
injecting a preposed protective slug as a sacrificial agent into the low-permeability oil reservoir to reduce the adsorption loss of the subsequent in-situ emulsified oil displacement agent slug;
injecting a slug of an in-situ emulsified oil displacement agent into the low-permeability oil reservoir, and starting residual oil and residual oil in an emulsifying mode on one hand; on the other hand, the micro sweep efficiency is improved by using the temporary pore throat blocking effect of the emulsion generated in situ;
and injecting an oil displacement agent into the low-permeability reservoir to displace residual oil and residual oil in the low-permeability reservoir.
The in-situ emulsification oil displacement method of the low-permeability oil reservoir can be carried out circularly for multiple times according to the actual needs of the target oil reservoir, and the production is finished when the economic limit yield is reached.
According to the in-situ emulsification oil displacement method for the low-permeability reservoir, the preposed protection slug is injected to serve as a sacrificial agent, so that the absorption and retention losses of the subsequent in-situ emulsification oil displacement agent slug can be well reduced.
In a specific embodiment of the invention, the chemical agent adopted by the front protective plug selects one of lignosulfonate solution, phosphate solution, silicate solution and carboxylate solution according to specific oil reservoir conditions. Wherein, the injection concentration of the preposed protective slug is 0.5 to 3.0 percent.
The injection amount of the front protective plug can be selected according to the conditions of the target oil reservoir. In one embodiment of the present invention, the pre-guard slug is preferably injected in an amount of 0.05PV to 0.25 PV.
In the in-situ emulsification oil displacement method of the low-permeability reservoir, the in-situ emulsification is realized with residual oil and residual oil in the oil displacement process through the limitation of the performance index of the in-situ emulsification oil displacement agent (not lower than a specified emulsification coefficient, not lower than a specified emulsion half-life period, not higher than the specified emulsion half-life period and not higher than the specified oil-water interfacial tension).
Emulsifying power means surfactant dissolutionEase of emulsification of the liquid with the crude oil. Under the condition of certain disturbance applied to the oil-water mixed system, the larger the amount and the higher the speed of the oil-water emulsion, the stronger the emulsifying capacity of the oil-water emulsion is. The oil-water emulsifying capacity is characterized by an emulsifying coefficient EI, and the larger the value is (EI is [0,1 ]]) The stronger the emulsifying capacity. With emulsion half-life t1/2The stability of the emulsion is represented, and the shorter the half-life is, the weaker the emulsion stability is (see the invention patent of ' high-temperature emulsification dynamic tester and test method ', ZL 201710261369.1 '; the enterprise standard of China oil and gas Co., Ltd. ' oil and water emulsification performance evaluation method ', Q/SY JD 97-2017).
In one embodiment of the invention, the in-situ emulsified oil displacement agent has an emulsification coefficient of not less than 0.5, an emulsion half-life of not less than 10min and not more than 40min, and an oil-water interfacial tension of not more than 10-1mN/m. Wherein the injection concentration of the slug of the in-situ emulsified oil displacement agent is 0.2 to 0.55 percent. The in-situ emulsified oil displacing agent consists of main agent 0.1-0.45 wt%, supplementary agent 0.05-0.25 wt% and water for the rest. Wherein the main agent is one or the combination of two of alkyl amide methyl betaine, alkyl amide propyl betaine and alkyl amide butyl betaine; the auxiliary agent is one or the combination of two of alkyl ether sulfate, alkyl alcohol sulfate and alkyl alcohol sulfonate.
The injection amount of the in-situ emulsified oil displacement agent slug can be selected according to the conditions of the target oil field. In a specific embodiment of the present invention, the injection amount of the slug of the in-situ emulsification oil-displacing agent is preferably 0.3 to 0.6 PV.
The in-situ emulsification oil displacement method for the low-permeability reservoir injects the in-situ emulsification oil displacement agent slug into the low-permeability reservoir and then injects the oil displacement agent.
In one embodiment of the invention, the oil displacement agent has viscosity of not higher than 2mPa · s and interfacial tension of not higher than 10-2mN/m surfactant aqueous solution or gas.
Wherein the injection concentration of the surfactant aqueous solution is 0.05-0.5%. The surfactant is one or the combination of two of alkyl sulfonate, alkyl benzene sulfonate and petroleum carboxylate.
The injection amount of the oil displacement agent can be selected according to the conditions of the target oil reservoir. In one embodiment of the present invention, the injection amount of the oil-displacing agent is preferably 0.3 to 0.8 PV.
Wherein the gas is CO2、CH4、N2One gas or a combination of two gases.
The in-situ emulsification oil displacement method of the low-permeability reservoir injects the in-situ emulsification oil displacement agent with strong emulsification capacity, weak emulsion stability and moderate low interfacial tension, and the in-situ emulsification occurs in the contact process of the in-situ emulsification oil displacement agent, residual oil and residual oil, on one hand, the residual oil and the residual oil are started in an emulsification mode; on the other hand, the Jamin effect of the emulsion generated in situ in the migration process is utilized to temporarily block the pore throat, and the micro sweep efficiency is enlarged. Meanwhile, the weak stability of the emulsion generated by in-situ emulsification is utilized to realize oil drop coalescence and oil wall formation, and the difficulty of demulsification treatment of the chemical flooding produced fluid is fundamentally eliminated and avoided. On the basis of temporary pore throat plugging, the oil displacement agent disclosed by the invention is low in viscosity, so that the oil displacement agent can enter residual oil and residual oil regions with lower permeability in an oil reservoir to drive crude oil in the oil reservoir.
The in-situ emulsion flooding method of the invention is different from the emulsion flooding method of injecting emulsion into an oil reservoir. The emulsion oil displacement method takes emulsion prepared on the ground as an oil displacement agent, the main performance requirement is the strong stability of the emulsion, and the main action range is near an injection well. The in-situ emulsification oil displacement method of the invention uses the surfactant solution as an oil displacement agent, the main performance requirements of the in-situ emulsification oil displacement method are strong emulsification capability, weak emulsion stability and moderate low interfacial tension of the surfactant solution, and the main action range is the deep part of an oil reservoir.
According to the in-situ emulsification oil displacement method for the low-permeability oil reservoir, the oil displacement efficiency of the low-permeability oil reservoir can be effectively improved through the synergistic effect of the sequential slugs.
Drawings
FIG. 1 is a flow chart of the in situ emulsion flooding method for a low permeability reservoir of example 1.
FIG. 2 is a dynamic curve of the emulsified oil rate of the oil displacing agent of example 1.
FIG. 3 is a graph showing the relationship between the emulsified oil content and the oil-water separation time of the oil-displacing agent of example 1.
FIG. 4 is a dynamic curve of interfacial tension for the oil-displacing agent of example 1.
FIG. 5 is a dynamic curve of the emulsified oil rate of the oil displacing agent of example 2.
FIG. 6 is a graph showing the relationship between the emulsified oil content and the oil-water separation time of the oil-displacing agent of example 2.
FIG. 7 is a dynamic curve of interfacial tension for the oil-displacing agent of example 2.
Detailed Description
The technical solutions of the present invention will be described in detail below in order to clearly understand the technical features, objects, and advantages of the present invention, but the present invention is not limited to the practical scope of the present invention.
Example 1
The embodiment provides an in-situ emulsification oil displacement method for a low-permeability reservoir, which comprises the steps shown in figure 1, and specifically comprises the following steps:
1. the used water is the simulated formation water of a certain low-permeability oil field, the mineralization degree is 3200mg/L, the used crude oil is the degassed crude oil of the oil field, the viscosity is 1.5mPa.s, and the oil reservoir temperature is 55 ℃.
2. The in-situ emulsified oil displacement agent consists of 0.15 percent of alkylamidopropyl betaine, 0.05 percent of alkyl alcohol sulfate and the balance of water, and the performance indexes of the in-situ emulsified oil displacement agent are shown in figures 2, 3 and 4. As can be seen from the figure, the in-situ emulsified oil-displacing agent has an emulsification coefficient of 0.713, an emulsion half-life of about 30min and an interfacial tension of 6.3X 10-3mN/m. The oil-displacing agent was 0.1% aqueous solution of alkylbenzenesulfonic acid salt (viscosity of 0.85 mPas, interfacial tension of 5.2X 10)-3mN/m)。
3. Columnar core (
10mD) oil displacement experiment process is that water is displaced to a residual oil state, 0.15PV 1% sodium phosphate solution is injected firstly, then 0.6PV in-situ emulsified oil displacement agent is injected, and the subsequent oil displacement agent is displaced. The water flooding displacement efficiency is 41.30 percent, the total displacement efficiency is 54.79 percent, and the displacement efficiency amplification is 13.49 percent％。
Example 2
The embodiment provides an in-situ emulsification oil displacement method for medium-viscosity crude oil of a low-permeability reservoir, which specifically comprises the following steps:
1. the used water is simulated formation water of a certain low-permeability oilfield, the mineralization degree is 3900mg/L, the used crude oil is degassed crude oil of the oilfield, the viscosity is 14.5mPa & s, and the oil reservoir temperature is 77 ℃.
2. The in-situ emulsified oil displacement agent consists of 0.35 percent of alkylamidopropyl betaine, 0.2 percent of alkyl ether sulfate and the balance of water, and the performance indexes of the in-situ emulsified oil displacement agent are shown in figures 5, 6 and 7. As can be seen from the figure, the in situ emulsified oil displacement agent has an emulsification coefficient of 0.609, an emulsion half-life of about 25min and an interfacial tension of 8.5X 10-2mN/m. The oil-displacing agent used was a 0.05% aqueous solution of a petroleum carboxylate (viscosity of 0.93 mPas, interfacial tension of 3.1X 10)-3mN/m)。
3. Columnar core (
50mD) oil displacement experiment process is that water is displaced to a residual oil state, 0.15PV 1% sodium phosphate solution is injected firstly, then 0.6PV in-situ emulsified oil displacement agent is injected, and the subsequent oil displacement agent is displaced. The water flooding oil displacement efficiency is 42.41%, the total oil displacement efficiency is 54.33%, and the oil displacement efficiency is increased by 11.92%.
4. Columnar core (
50mD) oil displacement experiment process is that water is displaced to a residual oil state, 0.15PV 1% sodium phosphate solution is injected firstly, then 0.6PV in-situ emulsified oil displacement agent is injected, and then CO is injected2And (5) driving. The water flooding oil displacement efficiency is 40.22 percent, the total oil displacement efficiency is 57.33 percent, and the oil displacement efficiency amplification is 17.11 percent.
5. Columnar core (
50mD) oil displacement experiment process is water displacement to a residual oil state, and surfactant displacement. The water flooding oil displacement efficiency is 39.23 percent, the total oil displacement efficiency is 44.37 percent, and the oil displacement efficiency isThe rate of increase was 5.14%.
Claims (7)
1. An in-situ emulsification oil displacement method for a low-permeability oil reservoir comprises the following steps:
injecting a preposed protective slug as a sacrificial agent into the low-permeability oil reservoir to reduce the adsorption loss of the subsequent in-situ emulsified oil displacement agent slug;
injecting a slug of an in-situ emulsified oil displacement agent into the low-permeability oil reservoir, starting residual oil and residual oil in an emulsifying mode on one hand, and improving microscopic sweep efficiency by using a temporary pore throat plugging effect of an in-situ generated emulsion on the other hand; the in-situ emulsified oil-displacing agent adopted by the in-situ emulsified oil-displacing agent slug has an emulsification coefficient not less than 0.5, an emulsion half-life period not less than 10min and not more than 40min, and an oil-water interfacial tension not more than 10-1mN/m; the injection concentration of the in-situ emulsified oil displacement agent slug is 0.2-0.55%;
injecting an oil displacement agent into the low-permeability reservoir to displace residual oil and residual oil in the low-permeability reservoir;
wherein, the in-situ emulsified oil displacement agent consists of 0.1 to 0.45 percent of main agent, 0.05 to 0.25 percent of auxiliary agent and the balance of water; the main agent is one or the combination of two of alkyl amide methyl betaine, alkyl amide propyl betaine and alkyl amide butyl betaine; the auxiliary agent is one or the combination of two of alkyl ether sulfate, alkyl alcohol sulfate and alkyl alcohol sulfonate.
2. The in situ emulsion flooding method of claim 1, wherein the pre-guard slug is selected from one of a lignosulfonate solution, a phosphate solution, a silicate solution, a carboxylate solution.
3. The in-situ emulsion flooding method of claim 1 or 2, wherein the pre-protection slug is injected at a concentration of 0.5% -3.0%.
4. The in-situ emulsion flooding process of claim 1, wherein the oil displacing agent is one having a viscosity of not more than 2 mPa-s and an interfacial tension of not more than 10-2mN/m surfactant aqueous solution or gas.
5. The in situ emulsion flooding method of claim 4, wherein the injection concentration of the aqueous surfactant solution is 0.05% -0.5%.
6. The in situ emulsion flooding process of claim 4 or 5, wherein the surfactant is one or a combination of alkyl sulfonate, alkyl benzene sulfonate, petroleum carboxylate.
7. The in situ emulsion flooding process of claim 4 wherein the gas is CO2、CH4、N2One gas or a combination of both.
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